A conventional illuminating device is disclosed in Patent Document 1. This illuminating device is provided with a diffusion plate diffusing light emitted from a light source, and a lens sheet is provided on a light-emission side of the diffusion plate. The lens sheet is a lenticular sheet formed of an array of a plurality of lenticular lenses (barrel-shaped lenses) having cylindrical surfaces.
The diffused light enters the lens sheet to be refracted by the cylindrical surfaces to be collected in a direction substantially perpendicular to the surface of the diffusion plate. In viewing a display panel disposed facing the illuminating device, this makes it possible to secure an ample amount of light emitted from the front surface of the display panel within a predetermined view angle, and to make effective use of light emitted from the light source.
In addition, part of light reaching the cylindrical surface from around a boundary between adjacent lenticular lenses enters the cylindrical surfaces at a large incidence angle to be reflected. This reflected light is emitted from a position facing the position at which the light has been reflected at a large angle with respect to a direction perpendicular to the front surface of a diffusion plate. To prevent this, a reflection sheet is disposed between the diffusion plate and the lens sheet. The reflection sheet has a plurality of reflection portions individually facing the boundaries between adjacent lenticular lenses.
As a result, light approaching boundaries between adjacent lenticular lenses is reflected toward the diffusion plate and then enters the lens sheet from other positions. This makes it possible to reduce the light that would otherwise be vainly emitted from the lens sheet at a large angle with respect to the direction perpendicular to the front surface of the diffusion plate, and thus to make an effective use of light emitted from the light source.    Patent Document 1: JP-A-2006-208930 (Pages 3-10, FIG. 1)
However, according to the above described conventional illuminating device, although light is collected such that the exit angle in the period direction of the lenticular lenses is within a predetermined range, the exit angle in the direction in which the lenticular lenses extend is large. FIG. 5 shows distribution of brightness of light emitted from the illuminating device. The vertical axis indicates the brightness, and the horizontal axis indicates the view angle of the lenticular lenses in the period direction (unit: °, indicated by the solid line A in the figure) and the view angle of the lenticular lenses in the direction in which they extend (unit: °, indicated by the broken line B0 in the figure).
According to the figure, for example, in the right-left direction of the display panel, light is collected within a range of a predetermined view angle, where the light amount becomes large. In the up-down direction of the display panel, however, the light amount does not differ much between in and out of the view angle. Thus, light is uselessly emitted out of the view angle in the up-down direction. Inconveniently, this reduces the light amount at the front surface, preventing fully effective use of light.
A feature of the present technology is to provide an optical member allowing more effective use of light emitted from a light source, and an illuminating device using such an optical member. Another feature of the present technology is to provide a display device and a television receiving device provided with an illuminating device capable of using light emitted from a light source more effectively.
To achieve the above, according to one aspect of the example embodiment presented herein, an optical member is provided with: a diffusion layer diffusing light emitted from a light source; a first light collection layer that is disposed on a light-emission side of the diffusion layer, that has a plurality of first projection portions extending in a direction and arranged with a predetermined period, and that refracts and collects light incident thereon from the light diffusion layer by using the first projection portions; a first reflection layer that has a plurality of first reflection portions so arranged, with a same period as the first projection portions, as to face boundaries between adjacent first projection portions, that is disposed between the diffusion layer and the first light collection layer, and that reflects light emitted from the diffusion layer by using the first reflection portions; a second light collection layer that is disposed on a light-emission side of the first light collection layer, that has a plurality of second projection portions extending in a period direction of the first projection portions and arranged with a predetermined period, and that refracts and collects light incident thereon from the first light collection layer by using the second projection portions; and a second reflection layer that has a plurality of second reflection portions so arranged, with a same period as the second projection portions, as to face boundaries between adjacent second projection portions, that is disposed between the first light collection layer and the second light collection layer, and that reflects light emitted from the first light collection layer by using the second reflection portions.
With this structure, light emitted from the light source enters the diffusion layer to be diffused. Light emitted from the diffusion layer enters the first light collection layer to be collected within a range of predetermined view angle by the plurality of first projection portions. Light emitted from the diffusion layer to travel close to the boundaries between adjacent first projection portions is reflected on the first reflection portions of the first reflection layer to return to the diffusion-layer side, and enters the first light collection layer from different positions. Light emitted from the first light collection layer enters the second light collection layer to be collected within a range of a view angle perpendicular to the first light collection layer. Light emitted from the first light collection layer to travel close to boundaries between adjacent second projection portions is reflected on the second reflection portions of the second reflection layer to return to the diffusion-layer side, and enters the second light collection layer from different positions.
According to the present embodiment, in the optical member structured as described above, it is preferable that a width of each of the second reflection portions in a period direction be smaller than a width of each of the first reflection portion in a period direction.
According to the present embodiment, in the optical member structured as described above, it is preferable that an axis extending in a direction in which the first projection portions extend and an axis extending in a direction in which the second projection portions extend form an angle of 90°±1°.
According to the present embodiment, in the optical member structured as described above, it is preferable that the first reflection layer, the first light collection layer, the second reflection layer, and the second light collection layer be adhered to the diffusion layer formed in a plate shape.
According to the present embodiment, in the optical member structured as described above, it is preferable that the first and second projection portions be lenticular lenses.
According to the present embodiment, in the optical member structured as described above, it is preferable that the first and second projection portions be prisms.
According to the present embodiment, in the optical member structured as described above, it is preferable that the first projection portions be lenticular lenses and the second projection portions be prisms.
According to the present embodiment, in the optical member structured as described above, it is preferable that the first projection portions be prisms and the second projection portions be lenticular lenses.
According to the present embodiment, in the optical member structured as described above, it is preferable that diffusion particles be dispersedly contained in a base material of the diffusion layer.
According to the present embodiment, in the optical member structured as described above, it is preferable that a thermal expansion coefficient of the diffusion layer be larger than a thermal expansion coefficient of the first light collection layer and a thermal expansion coefficient of the second light collection layer.
According to another aspect of the present embodiment, an illuminating device is provided with: the optical member structured as described above; a chassis to which the optical member is fitted; and a direct light source accommodated in the chassis.
According to another aspect of the present embodiment, an illuminating device is provided with: the optical member structured as described above; a chassis to which the optical member is fitted; and an edge-light type light source and a light guide plate accommodated in the chassis.
According to another aspect of the present embodiment, a display device is provided with: the illuminating device structured as described above; and a display panel disposed to face the illuminating device.
According to the present embodiment, in the display device structured as described above, the display panel is a liquid crystal panel in which liquid crystal is sealed between a pair of substrates.
According to another aspect of the present embodiment, a television receiving device is provided with the display device structured as described above.
According to the present embodiment, the first projection portions of the first light collection layer and the second projection portions of the second light collection layer are disposed perpendicular to each other, and the first and second reflection portions are provided corresponding to the boundaries between adjacent first projection portions and between adjacent second projection portions. This makes it possible to collect, without waste, light entering the first and second light collection layers in the period directions of the first and second projection portions within a range of a predetermined view angle. Thus, effective use can be made of light emitted from the light source.
According to the present embodiment, the width of each second reflection portion in the period direction is smaller than the width of each first reflection portion in the period direction. This makes it possible to reduce light emitted from the second light collection layer at an excessively large exit angle, and also to reduce light whose intensity is reduced by being reflected from the second reflection layer back to the diffusion layer. As a result, the light amount at the front surface can be further increased.
According to the present embodiment, since the axis extending in the direction in which the first projection portions extend and the axis extending in the direction in which the second projection portions extend form an angle of 90°±1°, effective use can be more securely made of light emitted from the light source.
According to the present embodiment, the first reflection layer, the first light collection layer, the second reflection layer, and the second light collection layer are adhered to the plate-shaped diffusion layer. This helps prevent creases from occurring in the first reflection layer, the first light collection layer, the second reflection layer, and the second light collection layer due to, for example, heat from the light source.
According to the present embodiment, since the first and second projection portions are lenticular lenses or prisms, the first and second projection portions for collecting light within a predetermined view angle can be realized easily.
According to the present embodiment, since diffusion particles are dispersedly contained in the base material of the diffusion layer, the diffusion layer for diffusing light can be realized easily.
According to the present embodiment, the thermal expansion coefficient of the diffusion layer is larger than the thermal expansion coefficient of the first light collection layer and the thermal expansion coefficient of the second light collection layer. Thus, when the optical member, whose periphery is fixed, expands due to heat from the light source, the light-emission side center portion becomes concave. This makes it possible to prevent the display panel and the optical member from coming in contact with each other.